Abstract

Humans are better at integrating desirable information into their beliefs than undesirable. This asymmetry poses an evolutionary puzzle, as it can lead to an underestimation of risk and thus failure to take precautionary action. Here, we suggest a mechanism that can speak to this conundrum. In particular, we show that the bias vanishes in response to perceived threat in the environment. We report that an improvement in participants' tendency to incorporate bad news into their beliefs is associated with physiological arousal in response to threat indexed by galvanic skin response and self-reported anxiety. This pattern of results was observed in a controlled laboratory setting (Experiment I), where perceived threat was manipulated, and in firefighters on duty (Experiment II), where it naturally varied. Such flexibility in how individuals integrate information may enhance the likelihood of responding to warnings with caution in environments rife with threat, while maintaining a positivity bias otherwise, a strategy that can increase well-being.

SIGNIFICANCE STATEMENT

The human tendency to be overly optimistic has mystified scholars and lay people for decades: how could biased beliefs have been selected for over unbiased beliefs? Scholars have suggested that while the optimism bias can lead to negative outcomes, including financial collapse and war, it can also facilitate health and productivity. Here, we demonstrate that a mechanism generating the optimism bias, namely asymmetric information integration, evaporates under threat. Such flexibility could result in enhanced caution in dangerous environments while supporting an optimism bias otherwise, potentially increasing well-being.

Footnotes

The authors declare no competing financial interests.

We thank Einar Jensen and the South Metro Fire Rescue Authority for providing resources and assistance for Experiment II; Jon Roiser, Oliver Robinson, Stephanie Lazzaro, Andreas Kappes, Caroline Charpentier and Sebastian Bobadilla-Suarez for helpful comments on earlier editions of this manuscript; Dominik Bach for advice on SCR collection and analysis.

This research was supported by a Wellcome Trust Career Development Fellowship to T. Sharot and a UCL Impact Award to N. Garrett.